Hi,
The way I should be using Element Buffer Objects is unclear to me.
If I use the following code:
Code:
osg::Geometry* polyGeom = new osg::Geometry();
polyGeom->setUseVertexBufferObjects(true);
osg::ref_ptr<osg::DrawElementsUShort> de = new
osg::DrawElementsUShort(osg::PrimitiveSet::TRIANGLE_STRIP,numIndices,myIndices);
polyGeom->addPrimitiveSet(de);
I expect the geometry to be using a VBO for vertex data *and* a VBO for index
data. However it seems only a VBO for vertex data is used, eg. the following GL
code is executed:
glBindBuffer(GL_ARRAY_BUFFER, &bufferid);
glBufferData(GL_ARRAY_BUFFER, ...);
glVertexPointer(3, GL_FLOAT, 0, offset_to_VBO);
glDrawElements(GL_TRIANGLE_STRIP, 4, ..., pointer_to_local_index_array);
No EBO is created then used in the last parameter in glDrawElements().
I am surprised this block of code above doesn't work as expected, as the
Geometry.cpp file looks like this:
Code:
bool Geometry::addPrimitiveSet(PrimitiveSet* primitiveset)
{
if (primitiveset)
{
if (_useVertexBufferObjects)
addElementBufferObjectIfRequired(primitiveset);
[ ... ]
I also tried:
de->setElementBufferObject(new osg::ElementBufferObject());
but still no luck.
Furthermore, I checked the osgparametric sample and something else is
disturbing me.
In this sample, when useVBO = true, createModel() calls
geom->setUseVertexBufferObjects(true), but still manually sets up:
1) a VertexBufferObject, that it binds to the vertices
2) an ElementBufferObject, that it binds to the primitiveset
Isn't the call to geom->setUseVertexBufferObjects(true) sufficient? Isn't that
the whole purpose of setUseVertexBufferObjects()?
I'm kind of confused here. Could somebody shed some light on this.
Thanks,
-F
------------------
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http://forum.openscenegraph.org/viewtopic.php?p=33987#33987
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